The present invention relates, in general, to an apparatus for screening and/or crushing screen materials, and more particularly to a screen crusher for use in a bucket of an earth moving machine, with the bucket being swingable about a horizontal rotation axis and including a back wall which is formed as screening bottom and supports screening shafts provided with screening elements.
German Pat. No. DE 93 04 186 U1 describes a screen crusher for soil materials for use in the bucket of an earth moving machine or a bucket loader. The bucket has a back wall formed as crusher screen with rotating shafts which extend substantially parallel to the rotation axis of the bucket. During screening operation, the bucket is swung about its axis of rotation so that the crusher screen is aligned substantially parallel to the ground. This screen crusher suffers the drawback that the drive assemblies for rotating the shafts are mounted laterally to the bucket. The lateral structural space that is required for accommodating the drive assemblies thus forms a dead space during operation, so that, for example, upon ingress of the bucket of the screen crusher into a silo, or along a building wall, the screen material situated between the side wall of the bucket and the building wall cannot be reached. Also, the housing of the drive assemblies is exposed to substantial wear and contamination. As a consequence, fastening screws of the covering plates become nondetachable when damaged or contaminated so that the screws or the covering plates must be removed. Maintenance and inspection of the drive assemblies are therefore significantly complicated.
A further drawback of this conventional screen crusher resides in the substantial length of the shafts which are thus exposed to great forces. Shaft bearings as well as drive assemblies must therefore be designed in a very robust fashion. However, in order to prevent the screen crusher from becoming too heavy, the torque being applicable is limited. As a consequence, in particular materials that are too large to penetrate through the screen and thus are difficult to crush prevent a complete filling of the bucket in view of the danger to overload the screen crusher. Moreover, the design of this conventional screen crusher causes during screening and/or crushing operation a hurling of rocks out of the bucket in a direction parallel to the rotation axis of the bucket and towards the operator's cab when the shafts rotate. Not only can this result in damage to the operator's cab but also exposes persons to harm. Therefore, the conventional crusher screen is highly suspect with respect to safety concerns.